1. Field of the Invention
The present invention relates to an organic light emitting device.
2. Discussion of the Background
Recent trends toward lightweight and thin personal computers and television sets have created a need for lightweight and thin display devices, and flat panel displays, such as liquid crystal displays (LCDs), that satisfy such requirements are being substituted for conventional cathode ray tubes (CRTs).
However, because the LCD is a passive display device, a back-light as a light source is needed, and the LCD may have various problems, such as a slow response time and a narrow viewing angle.
Among flat panel displays, an organic light emitting device may be the most promising as a display device for solving these problems.
The organic light emitting device includes two electrodes and an organic light emitting layer interposed between the two electrodes. One of the two electrodes injects holes and the other injects electrons into the light emitting layer. The injected electrons and holes are combined to form excitons, and the excitons emit light as they discharge energy.
Because the organic light emitting device is a self-emissive display device, an additional light source is not necessary. Therefore, the organic light emitting device may have low power consumption, as well as a high response speed, a wide viewing angle, and a high contrast ratio.
On the other hand, the organic light emitting device includes a plurality of pixels, such as red pixels, blue pixels, and green pixels, and images of full colors may be displayed by selectively combining these pixels.
However, the organic light emitting device has different light emitting efficiency according to light emitting materials. That is, a material having low light emitting efficiency among red, green, and blue may not be able to represent a desired color coordinate, and it may also be difficult to display a desired white color because white color is emitted by combining red, green, and blue.
To improve the light emitting efficiency, a micro-cavity may be used.
In a micro-cavity, light is repeatedly reflected between a reflection layer and a translucent layer that are spaced apart such that a strong interference effect is generated in the light. Accordingly, light of a specific wavelength is constructive, and light of the remaining wavelengths is destructive.
As such, the luminance and the color reproducibility may be simultaneously improved at the front side of the display panel.
However, when there is a micro-cavity, a color shift, in which a color viewed from the front side of the display panel is different from the color viewed from the lateral side of the display panel, is generated, and the color reproducibility may be reduced.